I’m leaning toward a short somewhere, since you said the PSU starts up with the paperclip but not when plugged in to the board.

I almost have an internal floppy drive also. It’s an internal Dell laptop drive that has a mini USB port for external use.

I actually found an A to A cable in my Big Box of Cables I Might Need One Day™ when trying to flash my Gotek floppy emulator with FlashFloppy firmware.